Sealing structures of many kinds are presently commercially available. Some are elastomeric, some are mechanical, and some, as with the present invention, may be a combination of mechanical and organic materials. In very high temperature embodiments, the embodiment herein disclosed may be provided without elastomeric components with successful application. The presently known most pertinent prior art U.S. Pat. Nos. are 1,721,325; 2,392,182; 3,098,660; 3,215,441; and 3,314,683.